Datsun 1600 HFS3-Help needed

Hey Richard,
The data you requested is listed below:

PIN - Pre Crank Voltage - Post Crank Voltage

1. 12.71 - 13.48
2. 0 - 0
3. 12.71 - 13.48
4. 4.50 - 0.06
5. 12.71 - 13.48
6. 0.54 - 0.55
7. 0.76 - 0.75
8. 0.02 - 13.48
9. 9.58 - 2.64
10. 0 - 0
11. 9.58 - 9.62
12. 12.02 - 13.48
13. 2.81 - 2.81
14. 0.24 - 0.18
15. 5.23 - 5.24
16. 5.60 - 0.08
17. 0 - 0
18. 4.95 - 0.07
19. 4.77 - 0
20. 2.38 - 2.32
21. 0.53 - 0.58
22. 2.40 - 2.40
23. 12.71 - 13.48
24. 0.01 - 0.01
25. 8.30 - 8.32
26. 4.64 - 4.65
27. 0 - 0
28. 2.57 - 2.57
29. 7.41 - 0
30. 0.88 - 0.76

[Richard L]

Thanks for the voltage, nice.

I can see the problem. Your 12V rail volatge is very low compared to a normal car. The H3 is comparing the rail voltage against the injector(-) voltage if it lower than 0.5V, it is considered as injector activation.

We have a few solutions:

1. Beefing up 12V cable size to the fuel pump and injectors. It is good practice anyway to have as little drop in voltage as possible.

2. Modifing the HFS-3 to allow a wider detection window. I think in your case, 2V is about correct.

I suggest doing solution #1 first, allowing the voltage on test pin#5 less than 0.5V.

Thanks Richard. I don’t yet fully grasp concept of how the H3 unit uses (+) and (-) voltage to trigger the system. As for the low rail voltage, is this pre or post cranking? My car has a pretty low idle. When I rev it up while taking the reading I saw over 14 volts at pins 5, 12 and 23.
Beefing up my fuel pump and injector cables poses a bit of a problem as it would require considerable modification to my wiring harness. I could possibly reduce the load been drawn by the fuel pumps by running them straight from the battery and using their current supply from the ECU to activate a relay. Would this solve the low rail voltage problem? If not the modifying the HFS-3 might be my only other option.
Cheers, Orlando

[Richard L]

Can you tell me the colour of the circuit board so that I can identify the version.

Let me a moment to work out the best way to tackle this.

Richard

[Richard L]

There is odd that you fuel injectior is not powered up at the pre-crank position.

Please re-locate the red wire of the grey connnector directly to fuel injector (+).

I?ll double check the circuit board when I get home and I?ll change the wire on the weekend.

Here is a quick recap of events so far:

(1) Installed HFS-3 unit. (+) and (-) input to unit both taken from injector number 2.
(2) Followed the start up guide to the letter. Everything worked as it should in this initial phase.
(3) Moved on to the system priming phase. Ignition to the pre crank position and gauge turned on. As soon as the delay passed and the gauge powered up the system activated and started spraying water.
(4) Tried several times, all with the same outcome. During the times the system was activated and spraying, the bar graph on the gauge never went past 2 bars. This was the same for both pre and post crank position.
(5)When away for a few weeks. Did some head scratching and some research while I was gone. Came Across and few wiring diagrams on this forum which showed the (+) input taken from the computer 12 volt ignition supply. So I changed mine to match that configuration when I came back.
(6) Gave the system a thorough going over. Powered it up and the same happened as I've explained at number 4.
(7) Left the gauge on and turned the ignition off and back on again. This time the gauge didn?t light up as it had done previously. The only light it displayed was the yellow water level LED. The system did not activate and hasn?t since.

The circuit board is black.

Richard, I'm not sure if it will help but just in case here is the link to the manual for my ECU. http://www.mrm-racing.se/bag/SM4MANUAL.pdf
The wiring diagram is on page 128. The only difference to the wiring on my car is that I now run the Autronics CDI unit. I'll see in I can find and wiring diagram for that too just incase.
Cheers, Orlando

CDI Info and wiring:
http://www.mrm-racing.se/bag/500R%20...%20Oct2009.pdf
http://www.mrm-racing.se/bag/DFCDI%20BASIC%20WIRING.pdf

[Richard L]

One step at a time...

Can you check the voltage at the injector(-) Pin#8 at pre-crank position. It should have 12V there.

According to the test voltages above, it showed near 0 volt!